CCT is a number, measured in degrees Kelvin, that helps to describe the relative warmth or coolness of a light source. Most light bulbs will range from 2700K (warm, incandescent color) to 5000K or higher.
For most residential applications, 2700K and 3000K are preferred color temperature options as they both create a nice, warm appearance that creates an inviting and relaxing environment. Some prefer 4000K and even 6500K. Selection is the taste of purely customers.
For retail or commercial applications, 4000K is a popular color option as it provides for a crisper, more energetic shade of white. For industrial or task-oriented applications, 5000K or even 6500K is a preferred color option, as these color temperatures best match natural daylight. Optimal Light has all these color options for most of the products.